While slowing to turn or stop the engine occasionally stalls. Weary of the problem I have noticed that when slowed below 5mph the RPM will hunt around 800 and settle to 500 or lower.
I disconnected the battery last week while changing the oil/filter and the air filter. Re-connected and performed a relearn for the computer. This has had no effect on the problem, but I have noticed it will happen more often after driving harder than normal (acceleration). The engine behaves as it should at idle and driving city or highway, has only stalled when slow to a stop. 265K miles.

 

sounds like a vacuum leak to me.

 

Try cleaning the maf and throttle body.

 

Sunday morn, I cleaned the MAF which had a layer of grey film on with CRC Elect, and acid brushed with alcohol. Inspected visible vacuum lines under the hood and the seemed to be in very good condition and secure, looked for a layout diagram on line so I could check all but of course typing in for something pertaining to a vehicle I got hundreds of hits on great car deals and loans but not what I was looking for.
Relearned the computer and took for a test flight, and it drove well but idle speeds and cornering it still wanted to idle around 500 rpm and stalled once at a stop sign. Drove it around 45 minutes on country roads later in the day and it seemed to improve and the idle speed seemed to now be around 600, I do not have a chart to give the normal operating characteristics but I would assume the idle should be 700 or better on an automatic transmission. Another note is that my gas mileage appeared to improve 12.5 to 14 which may be a good sign. Today I shall pull the air box and get to the Throttle body and maybe some more vacuum lines will be visible.

 

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Wow!! Relearned the computer and then went for a drive and the difference was unbelievable. Smoothest acceleration and deceleration ever for the truck, the idle still seemed a bit low but the throttle response was remarkable. The idle hunting is gone and the rpm's are very solid and consistent while slowing to stop or corner. The build up was so thick that there was barely any sunlight visible around the butterfly.